Security for Customer Portals
Customer portals give clients self-service access to their accounts, documents, and billing. They expose sensitive data directly to end users, making access control and data isolation critical.
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Why Security Matters for Customer Portals
Customer portals are the most common target for IDOR attacks. Each customer has their own data, and the portal must ensure they can only see theirs. AI-generated portal code frequently uses predictable URLs or sequential IDs that allow customers to access each other's accounts. Self-service features like password reset, billing management, and document download each introduce additional attack surfaces.
Security Risks
Customer data cross-access (IDOR)
criticalCustomers accessing other customers' invoices, documents, or account details by changing IDs.
Mitigation
Verify resource ownership on every request. The authenticated user must be the owner of any resource they access. Use UUIDs instead of sequential IDs.
Insecure password reset
highPassword reset tokens that are predictable, don't expire, or are reusable.
Mitigation
Use cryptographically random reset tokens with short expiry (15 minutes). Single-use only. Send via email, never expose in URLs that might be logged.
Document access without authorization
highShared document links that don't verify the requester's identity.
Mitigation
Require authentication for all document access. Use signed URLs with short expiry for document downloads. Log all document access.
Security Checklist
Every data request verified against the authenticated user's account.
Cryptographically random tokens, short expiry, single-use, email delivery only.
Verify user permission before serving any document or file.
Use UUIDs instead of sequential IDs to prevent enumeration.
Show customers their recent login activity. Log all account changes.
Require re-authentication for payment method changes.
Real-World Scenario
An accounting firm builds a client portal using Replit where clients download their tax documents. Documents are stored at /api/documents/{id} with sequential IDs. A client changes the ID from 1547 to 1546 and downloads another client's tax return containing SSN, income details, and bank account numbers.
Frequently Asked Questions
How do I prevent customers from seeing each other's data?
Verify resource ownership on every API request. When a customer requests /api/invoices/123, check that invoice 123 belongs to the authenticated customer. Use RLS policies as a database-level safety net.
Are sequential IDs a security risk?
Yes. Sequential IDs make enumeration trivial — just increment the number. Use UUIDs (e.g., 550e8400-e29b-41d4-a716-446655440000) which are not guessable. However, always verify ownership regardless of ID format.
How should password reset work?
Generate a cryptographically random token, store its hash in the database with a 15-minute expiry, and email the token as a link. On use, verify the token, expire it, and require a new password. Never reuse tokens.
Security for Other Use Cases
Secure Your Customer Portals
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